Process of producing calcium cyanamid.



UNITED T5 all a mama, concern:

13 .1 wknbwn that I, JOHAN HJALMAR Iirnuomi, a citizeriof the Kingdom of Sweden, residing at London, Great Britain, have invented' n'ew and useful Improvements in Processe' ot Broducing Calcium Cy anamid, "of which the following is a specification. a i

Asis"well'knowh, calcium cyanamid is rdduc'ed-by heating calcium carbid or a mixture of burnt lime and coal in suitable proportions to a su-itable temperature while nitrogen is' suppliedt The formation of calciumjcyanamid fromcalcium carbid and n1- trogen =may-be expressed by the following formular It-isnvell-known' that this process has not yet'reachedits technical perfection, but is still suffering from certain inconveniences which'havefi hitherto not been overcome.

Thus for}: instance the above mentioned reaction does'fn'ot take place so completely that a qua ntit ative output is. obtained.

From theoretical point ofview, the carbid of the market containing 70*per cent. of

pure carbid should give calcium-cyanamid containing 23.4 per -cent. of nitrogen. In

reality, such an output has, however, never been obtained in the industrial application;

at the most a percentage of nitrogen of 20 per cent. has been attained. Moreover, such a high percentage has been attainable only by such an abundant supply of nitrogen that the process becomes unecon'omical.

When the above named reaction takes total consumption of nitrogen.

In order toincrease the output and at the same time to accelerate-the reaction, proposals have been made to use additions acting catalytically,preferably calc um chlOIld and calcium fluorid; byflmean's of which the absorption of nitrogen is facilitated, and'the ,roaction under such; circumstances is caused.

Specification of Letters Patent.

seawat r sai-mum.

Patented Jan. 19,1915.

Application filed February 14., 1914. Serial No. 818,787.

to take place at. lower temperatures than otherwise. I

Proposals have also been made to supply for the same purpose the nitrogen at a, high ovelpressure by means of which the reaction may be accelerated essentially. andithas even been proposed to use high pressure on the nitrogen and atthe, same time to add to the carbid substances acting cata lyticall v,-in

order to still more a ccelera te the reaction. a :In

applying the said methods industrially it has, however, oeen found that the output of cyana'mid is far from quantitative; This probably depends on the fact that if the re-' action which proceeds exothermically be 'accelerated too much, such an increase of the temperature will occur at, certain pointsthat' the calcium cyanamid formed will melt] or 'sinter and on account thereof the nitrogen will be prevented from penetrating completelv into the carbid. It has also been found, when breaking the blocks-of cyanami'd into pieces, that they contain larger or smaller balls of untransformed calcium carbid embedded in the mass of cyanamid.

-.The present inventionrelates to a process of producingnalcium cyanamid by means of which all the inconveniences 'mentioned above will be obviated or at least be con sidera-bly reduced. The invention is based on'the observation that the reaction between the nitrogen and the calcium carbid, may be caused to proceed with a great output, if the nitrogen be supplied 'atan overpressure,

and the carbid at the same time-diluted by inactive substances added in such a quantity, that the temperature" of the mass of carbid is. prevented, during the proceeding of the reaction, from reaching-the temp'erature of sintering of the calcium cyanamid.

The degree of dilution of'the carbid by active substances depends upon the magni-' tude of the overpressure used. #It may by vway of example be mentioned thatlthe-in- .ventor, in using a carbid containing 60 per cent; CaC only and an overpressure 'of 1 1 atmosphere, has obtained calcium cyanamid 'contaming 20 per cent. nitrogen, the loss of nitrogen, when ventilating theiurna ce of reaction, amounting to 20 per cent. only of the total consumption'of nitrogen. By usinga higher overpressure the percentage of CaC of the carbid used may 'be'reduced successively, so that, in using an overpressure of 5 to 10 atmospheres, a percentage of 5-5 to 50 per cent. of CaC .will give the best results. The dilution of the carbid ma be effected either by producing initially 'a carbid of low percentage or by diluting'a c'arbid of high percentage by inactive substances,-'as for instance sand, 'or the like. r a

The improved effect attained by the present invention may be explained by'this that the supply of nitrogen at an overpressureexerts,'an accelerating influence upon the re action, said influence being'the stronger, the

higher is the pressure used, whereas the inactive additions absorb heat and thus pre-- 've'nt the temperature, in spite of the speedier proceeding of-reaction, from reaching at any p"oint of the mass the temperature of siTn-tering of the calcium cyanamid. Therefoiith percentageofinactive additions is 3 r 3 to be taken in acertain proportion-"to the overpressure used and the speed ofreaction paused thereby, which proportion may be easily'found by experiments foreachseparate type of furnace and each separate kind of carbid used The fact that the, consumption ofnitrogen for ventilating-of the furnace may be re duced as considerably as is'evide'nt from theexample stated above, may be explained, on the one side, by this that the controlling of the temperature of the furnace eflected by means of the present invention reduces the formation of noxious gases in the furnace,'and, on the other side, by,th1s that the overpressure exerted upon the nitrogen reduces the noxious influence of the gases formed uponthe proceeding of thereaction.

The results obtained bymeans of the invention prove that the general opinion that,

in producing calcium qvanamid,"a carbid of a percentage as high as possible-is to be used, is not correct, in as mu'c'h as the come 1 paratively low outputs hitherto-attained are caused even by .the'too strong increase of temperature due to'an'accelerated reaction in a mass of carbid of high percentage; Further, the present inventionlms proved that a suitable-adjusting of the pressure of the nitrogen renders all additions of catalytic substances dispensable and will even increase "considerably the-output, if, at the.

same t'ime,by diluting correspondingly the carbid, the, temperature is prevented from rising at certain'pointsorih larger portionsof the mass-on account of the heat developed during the reaction.

- Having now described myinvention, What 1' clalm as new and'jdesire to secure byLetters' Patent is:

containing a percentage, of heat absorbing,

. but otherwise' inactive substances to a suitable temperature, and supplying the nltro- The process ofrproducing calcium cyanamldjfrom 'calclum carbid. and nitrogen, whlch consists in heating calclum carbld gen to the calcium carbid at an overpres- I claim the foregoing 

